The production of animal cell lines with high productivity is related with an industrial utility value of the corresponding target protein to be produced, and a process therefor takes a long time and high costs. The first thing to consider when producing animal cell lines with high productivity is to produce a vector for efficiently expressing a recombinant protein to be produced. How to produce the structure of the vector may greatly influence the obtainment of production cell lines with a higher value in the future. The expression of a foreign gene inserted into animal cells becomes stable as it is inserted into chromatin. The expression rate may vary depending on the position inserted, and this may also affect the growth or metabolism of cells. The foreign gene inserted into the chromatin sometimes becomes extinct as time passes by. Thus, various researches have been conducted for minimizing the decrease in gene expression, and sorting the cell lines with an increased expression rate to the maximum. Additionally, the modification of the structure of the vector is known to have a great impact thereon.
One of the methods showing enhanced effects while maintaining the gene delivered from the outside in the cells is to use a cis-regulatory element. When introducing a gene which encodes a target protein into the cells by using the vector including the cis-regulatory element, the expression of a target protein may be maintained regardless of the insertion position of chromatin, and a role for enhancing expression may be performed. As representative examples, there are matrix attachment regions (MARs), universal opening elements (UCOEs), locus control regions (LCRs), insulator elements, stabilizing and anti-repressor elements (STARs), etc. The construction and application of a vector system using each gene element have been considered a very major field (Nature biotechnology, Vol. 29, 593-597, 2011).
Only an expression augmenting sequence element (EASE) is known as the cis-regulatory element originated from a gene of CHO cell, which is widely used as a therapeutic protein production cell line. Other than the EASE, the cis-regulatory element has been found in a gene originated from human or mouse through various methods. The EASE was discovered by finding out the genetic position of a vector inserted into the production cell line which expresses a great amount of Tumor Necrosis Factor Receptor (A E Morris et al., Animal cell technology, 1997). Most of the cis-regulatory elements discovered in the past are used industrially and commercially in companies which produce biopharmaceuticals. Thus, screening a new cis-regulatory element originated from the CHO cell gene by a method different form the past and possessing a recombinant vector including the same would be useful for a process of developing various biopharmaceuticals such as biosimilars, etc.